U.S. patent number 6,621,782 [Application Number 09/368,359] was granted by the patent office on 2003-09-16 for optical disk, an optical disk device, and a method of managing defects in an optical disk.
This patent grant is currently assigned to Mitsubishi Denki Kabushiki Kaisha. Invention is credited to Kazuhiko Nakane, Hiroyuki Ohata.
United States Patent |
6,621,782 |
Nakane , et al. |
September 16, 2003 |
Optical disk, an optical disk device, and a method of managing
defects in an optical disk
Abstract
When optical disk defects are managed by using non-defective
areas in place of defective areas, different criteria are used for
detecting the defects, depending on the type of data recorded on
the disk. For example, to avoid interruptions of real-time
recording, less strict criteria are used when audio or video data
is recorded than when computer data is recorded. The criteria
themselves may also be recorded on the disk.
Inventors: |
Nakane; Kazuhiko (Tokyo,
JP), Ohata; Hiroyuki (Tokyo, JP) |
Assignee: |
Mitsubishi Denki Kabushiki
Kaisha (Tokyo, JP)
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Family
ID: |
16775580 |
Appl.
No.: |
09/368,359 |
Filed: |
August 5, 1999 |
Foreign Application Priority Data
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Aug 5, 1998 [JP] |
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10-222003 |
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Current U.S.
Class: |
369/53.1;
369/47.1; 369/53.12; 369/53.15; G9B/20.046; G9B/20.053 |
Current CPC
Class: |
G11B
20/18 (20130101); G11B 20/1833 (20130101); G11B
7/00745 (20130101); G11B 20/1254 (20130101); G11B
20/1883 (20130101); G11B 20/1889 (20130101); G11B
2020/10537 (20130101); G11B 2220/20 (20130101) |
Current International
Class: |
G11B
20/18 (20060101); G11B 7/007 (20060101); G11B
20/12 (20060101); G11B 007/00 () |
Field of
Search: |
;369/47.1,47.14,53.1,53.11,53.12,53.13,53.15,53.16,53.17,53.2,53.37,53.45,59.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0642128 |
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Mar 1995 |
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EP |
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0822555 |
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Feb 1998 |
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EP |
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0952573 |
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Apr 1999 |
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EP |
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9-45011 |
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Feb 1997 |
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JP |
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63A 14379 |
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Jan 1999 |
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JP |
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11144381 |
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May 1999 |
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JP |
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WO9417524 |
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Aug 1994 |
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WO |
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Other References
G Bouwhuis et al, Philips Research Laboratories, Eindoven, Oct. 31,
1985, pp. 248-265..
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Primary Examiner: Edun; Muhammad
Claims
What is claimed is:
1. A method of managing defects on an optical disk used for
recording data, comprising: determining criteria for detecting
defects according to the type of data for which defects are to be
detected; and detecting defects using said criteria when data is
recorded on or reproduced from said disk, wherein said step of
determining criteria includes: providing a plurality of criteria;
and selecting one of said plurality of criteria according to the
type of data for which defects are to be detected.
2. A method of managing defects on an optical disk used for
recording data, comprising: determining criteria for detecting
defects according to the type of data for which defects are to be
detected; and detecting defects using said criteria when data is
recorded on or reproduced from said disk, wherein said criteria
include at least first criteria and second criteria, said second
criteria being less strict than said first criteria, wherein said
method further comprises: selecting one of said first criteria and
said second criteria, said step of selecting including selecting
said first criteria when the data for which defects are to be
detected is one for which time restriction with regard to data
recording or reproduction is less strict, and selecting said second
criteria when the data for which defects are to be detected is one
for which time restriction with regard to data recording or
reproduction is more strict.
3. A disk device for accessing data on an optical disk, comprising:
means for determining criteria for detecting defects according to
the type of data for which defects are to be detected; and means
for detecting defects using said criteria when data is recorded on
or reproduced from said disk, wherein said determining means
comprises: means for storing a plurality of criteria; and means for
selecting one of said plurality of criteria according to the type
of data for which defects are to be detected.
4. A disk device for accessing data on an optical disk, comprising:
means for determining criteria for detecting defects according to
the type of data for which defects are to be detected; and means
for detecting defects using said criteria when data is recorded on
or reproduced from said disk, wherein said criteria include at
least first criteria and second criteria, said second criteria
being less strict than said first criteria, wherein said device
further comprises: selecting means for selecting one of said first
criteria and said second criteria, said selecting means selecting
said first criteria when the data for which defects are to be
detected is one for which time restriction with regard to data
recording or reproduction is less strict, and selecting said second
criteria when the data for which defects are to be detected is one
for which time restriction with regard to data recording or
reproduction is more strict.
5. An optical disk for recording data, comprising: an area storing
criteria control information specifying criteria to be used for
detecting defects for data recorded on or reproduced from the disk,
wherein said criteria control information is selected from a
plurality of predetermined criteria.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method of managing defects in a
disk recording medium, an optical disk device recording data on the
optical disk using such a defect management method, and an optical
disk capable of storing information concerning a defect criteria
used for replacing a defective area of disk with a non-defective
area.
A very high degree of reliability less than 10.sup.-12 at worst is
required of a disk used for recording computer data.
Defect-managing systems have been used hitherto to accommodate the
reality that defects in recording sectors which lead to an error
are unavoidable, even very rare, in the current disk-manufacturing
technique.
Disk mediums are subjected to the defect management for assuring
data reliability even when dirt, scratches or degradation due to
repetition of rewriting operation is caused. Primary defects
occurring at the time of manufacture of the disks are found through
a certifying process carried out at the time of initializing disks,
and secondary defects occurring after being put to use are found
through verification carried out at the time of writing, or the
like. Sectors found to have a defect are replaced, using sectors
located in a spare area formed on part of a disk other than a user
area. In the defect management, a pair of a user area and a spare
area is called a group.
In an example of arrangement of user areas and spare areas on a
disk, the data area consists of a single group. However, there are
many optical disks in which a data area is divided into a plurality
of groups. When a defective group is found in a group, it is first
attempted to replace the defective sectors using sectors in a spare
area of the same group. In many cases, an optical disk is
configured such that a recording capacity of a spare area is
several % of that of a user area. The 90 mm magneto-optic disk
standard defined by ECMA-154 or ECMA-201, and the DVD-RAM standard
defined by ECMA-272 are examples of such configuration.
Incidentally ECMA is an abbreviation of European Computer
Manufacturers Association, DVD is an abbreviation of digital video
disk, and RAM is an abbreviation of random-access memory.
The presence or absence of a defect in a sector can be determined
by an error in an ID signal representing a physical address of the
sector, an error in a recorded data signal, or a servo error
signal.
When a plurality of ID's are recorded in the header area for each
sector, if not less than a predetermined number of ID's for each
sector contain an error, the sector in question is found have a
header defect. In the DVD-RAM standard for example, each sector is
provided with four ID's, and an error can be detected for each ID.
Each sector is found not to have a header defect if it has not more
than two ID errors: a sector having three or more ID errors is
found to have a header defect, since its reliability is low.
Further, the presence or absence of an error in a recorded data
signal is detected by the use of an error correcting code added
thereto. When more than a predetermined number of errors are
included per unit of recording, the data signal is found to have a
data defect. The "unit of recording" may be a sector or a block
constituted of a plurality of sectors depending on the span of an
error correcting code (ECC).
In the DVD-RAM standard, data is recorded in sectors on a disk, and
is subjected to error-correcting coding in units of 16 sectors,
called an ECC block. Data of 32 KB constituting one ECC block is
arranged in the form of matrix of 172.times.192 bytes (or 172
columns.times.192 rows), and Reed-Solomon codes (inner code PI,
outer code PO) of 10 bytes and 16 bytes are added in column
direction and row direction, respectively, to constitute a product
code.
The inner code PI is disposed so as to be completely within a
sector. By means of the inner code PI, the number of error bytes in
each row of the reproduced data can be determined. In accordance
with the detected number of errors, reliability of each row is
evaluated, and whether each sector or each block has a data defect
can be determined based on the number. For instance, a sector
including four or more rows having four or more error bytes is
found to be have a data defect, or a block including six or more
such rows are found to have a data defect.
With regard to detection of defects based on a servo error signal,
when the magnitude of the servo error signal such as a tracking
error signal exceeds a predetermined value that makes it difficult
to ensure the servo control stability required of data recording, a
sector in question is found to have a servo defect.
When a sector is found to have a header defect, a data defect or a
servo defect, it is found to be defective.
Generally, in the defect management, two different methods are used
for performing replacement of a sector. One is a slip replacement,
and the other is a linear replacement.
The slip replacement is applied to primary defects. If a defective
sector is found at the time of certifying a disk, the next sector
is used in place of the defective sector. In a disk drive device,
for accessing a sector containing data, a logical address is
converted into a physical address representing the position of the
sector, and a sector having ID's representing the physical address
is accessed. When the slip replacement has been performed, the
physical address numbers corresponding to the logical addresses are
shifted, or "slip" by one.
The slip replacement is carried out within each group. For
instance, if there occur two slip replacements of m sectors and n
sectors in a user area, the end of the user area of the group is
shifted into the head of the spare area by (m+n) sectors. If such
slip replacements are made, the linking relation between the
physical addresses and logical addresses is shifted by the number
of replaced sectors for all the sectors succeeding the replaced
sectors. Primary defects subjected to the slip replacement are
registered in a PDL (Primary Defect List). The list contains the
physical addresses of defective sectors in each entry.
Linking the physical addresses with the logical addresses can be
made only when a disk is initialized, and therefore, the slip
replacement is applied to primary defects only.
The linear replacement is applied to secondary defects. When a
defective sector is found, replacement is effected using spare
sectors in a spare area. When an ECC block (formed of 16 sectors)
is found to contain a defective sector, the entire ECC block is
replaced with 16 sectors in a spare area. There may be a case where
a block in a spare area having replaced another block is
subsequently replaced with another block. A substitutive sectors
are given the same logical addresses as the original sectors.
The linear replacement is effected within the same group first. For
instance, when two linear replacements of m blocks and n blocks
respectively occur in a user area, m blocks and n blocks at the
beginning of the unused part of the spare area are used. It may be
so designed that when the spare area of the same group has been
used up the spare area in another group is used. Secondary defects
subjected to linear replacement are registered in an SDL (Secondary
Defect List). The list contains physical addresses of defective
sectors and substitutive sectors in each entry.
When such a linear replacement has been made, every time an access
is made using a logical address which designated a substitutive
sector, an access to the substitutive sector and subsequent return
have to be made. Therefore, the average data transfer rate is
substantially lowered when the secondary defects exist.
A set of the defect lists PDL and SDL is stored in a defect
management area within a control information area in each of outer
and inner periphery parts. They are disposed at a plurality of
locations, and they are recorded together with information on the
structure of a disk.
Generally, in recording devices, criteria for detecting primary and
secondary defects are set in the following way.
A disk is at its best condition when primary defects are detected
and registered. The number of defects on the disk increases with
time or usage due to scratches and dirt, and resultant degradation.
Therefore, the primary defects are detected and replacement is
effected by using a criteria which is more strict than that for
detecting the secondary defects, so that some additional scratches
or dirt will not results in the finding of a defect according to
the criteria for detecting the secondary defects.
Although the secondary defects are detected with a criteria which
is less strict than that for the primary defects, a margin of
safety is left between the criteria for detecting the secondary
defects and the error-correcting capability, so as to ensure error
correction during reproduction. In this way, different criteria are
used for the primary defect detection and the secondary defect
detection.
Conventionally, optical disks are used mainly for computer date
recording, and therefore, the primary concern was to improve the
data reliability, and defect management mainly consisting of
replacement using spare sectors has been developed to deal with the
defects in the recording sectors causing the errors.
In recent years, with increasing capacity of optical disks, their
uses are expanding to the video recording field, such as in
DVD.
Data files for recording computer data (PC files) are expected to
be completely error-free, and high reliability is required of
recording. In contrast, data files for recording audio or vide data
(AV files) require recording data inputted continuously in real
time. In some cases, errors are permissible as long as the
disturbance of reproduced images or sounds is not noticed, so that
data reliability is not required to be as high as in computer data
recording. Instead, non-interruption of recording is important.
That is to say, with regard to storage devices for computer data
recording, primary importance is the reliability rather than
recording time, while, for storage devices for video recording,
primary importance is continuous recording performance.
Consequently, in case of using the same type of disk for recording
both audio or video data and computer data, it is required to
ensure reliability and recording speed which meet the requirements
of the respective recordings. Likewise, defect management must be
adaptable to both types of recording.
Conventional defect management for optical disks has the following
drawbacks.
For carrying out replacement to deal with secondary defects of a
disk at the time of recording, data is reproduced from the recorded
part for verification, and if errors of more than a prescribed
criteria, or a defective part from which reproduction is impossible
is found, the data recorded in that part is re-recorded in
substitutive sectors in a spare area, and data is again reproduced
from the substitutive sectors for verification. Thus, when a
secondary defect is detected, and replacement is effected, the time
needed is four times more than the time needed for recording data
once. In case of recording audio or video data in real time, it is
likely that recording is interrupted if a defect is detected.
One solution to this problem is not to detect secondary defects
during the recording of audio of or video data. In this case, the
reproduced image or the like may have disturbances at parts having
the secondary defects, but such disturbances are considered less
objectionable than interruption of recording. The underlying
assumption is that once primary defects have been removed at the
time of initialization of the disk, any secondary defects that
might occur will be minor. If the scale of the secondary defects is
greater than predicted, the disturbance of the reproduced picture
may be intolerable, and thus this solution fails.
Where the optical disks are used for recording audio or video data,
it is considered unnecessary to detect defects with criteria which
is as strict as that used in recording computer data. This is
because, if the excessively strict criteria is used, sectors which
are permissible for audio or video data are also found defective,
and video recording is interrupted when the time-consuming
replacement is effected. Because the conventional defect management
method does not take into consideration the intended use of the
optical disk, and the criteria used is of the same level regardless
of the intended use of the optical disk, there was no conception of
using the optimum defect detecting method.
SUMMARY OF THE INVENTION
The present invention has been made overcome the above-outlined
problem, and its object is to adapt defect management to the type
of data recorded on an optical disk, or the intended use of the
disk.
Another object is to improve the interchangeability of the optical
disk.
A further object is to improve the utility of optical disks for
recording audio or video data.
According to a first aspect of the invention, there is provided a
method of managing defects on an optical disk used for recording
data, including
determining a criteria for detecting defects according to the type
of data for which defects are to be detected; and
detecting defects using the criteria when data is recorded on or
reproduced from said disk.
With the above arrangement, it is possible to use the criteria
suitable for the particular type of data for which defects are to
be detected.
The step of detecting defects may be performed with regard to data
recorded on the disk.
In this case the defects may be detected when the data is recorded
on the disk, or when the data is reproduced for verification of the
data having been recorded. When the defects are detected when the
data is recorded, determination of presence or absence of servo
defects and header defects can be made, but determination of
presence or absence of data defects cannot be made. When the
defects are detected during reproduction for verification, presence
of absence of data defects as well as servo defects and header
defects can be determined.
The step of detecting defects may alternatively be performed when
the data is reproduced. In such a case, if defects are detected,
the reproduction of the data is re-tried. Decision on whether the
reproduction is to be re-tried is made using different criteria
depending on the type of data being reproduced.
The method may further comprise the step of using non-defective
areas of the optical disk in place of defective areas of the
optical disk.
With the above arrangement, the result of the defect detection can
be used in making a decision as to whether the areas found to be
defective should be replaced with non-defective areas.
The step of determining a criteria may include:
providing a plurality of criteria; and
selecting one of the plurality of criteria according to the type of
data for which defects are to be detected.
With the above arrangement, the defect criteria can be determined
simply by providing a signal which selects one of the plurality of
criteria provided in advance, rather than specifying the values
forming the criteria.
The plurality of criteria may include at least a first criteria,
and a second criteria, the second criteria being less strict than
the first criteria, and said step of selecting may include
selecting the first criteria when the data for which defects are to
be detected is one for which time restriction with regard to data
recording or reproduction is less strict, and selecting the second
criteria when the data for which defects are to be detected is one
for which time restriction with regard to data recording or
reproduction is more strict.
An example of the data for which time restriction with regard to
data recording or reproduction is less strict is computer data. An
example of the data for which time restriction with regard to data
recording or reproduction is more strict is audio or video
data.
By using a less strict criteria for the audio or video data,
interruption of the audio or video data recording is avoided unless
the defect is of such a degree that the resultant disturbance in
the sound or picture is intorerable.
The method may further include sending control information for
specifying the criteria, from means for processing data to be
recorded, to means for recording said data.
The above-mentioned means for processing data to be recorded is for
example a host device. The above mentioned means for recording the
data is for example a disk device.
With the above configuration, the host device can set criteria
which is finely optimized for the type of the data to be recorded
on the disk.
The data may be recorded in units of recording, and the step of
sending control information may send the control information for
each each unit of recording.
With the above configuration, it is possible to dynamically set
criteria which is finely optimized for each unit of recording
(e.g., sector or ECC block), depending on the type of the data to
be recorded in each unit of recording. That is, even when different
types of data, e.g., audio or video data, and computer data, are
both recorded on the same disk, since the host device sends the
criteria control information in association with the data to be
recorded, and the defect management can be effected using the
optimum criteria for the respective data.
The control information specifying the criteria may select one of a
plurality of criteria.
With the above configuration, the amount of control information is
small, since it only needs to specify one of the plurality of
predetermined criteria, rather than specifying values forming the
criteria itself.
Data may be recorded in units of recording, and said method may
further include recording control information representing the
criteria for each unit of recording, on the optical disk, in
association with each unit of recording.
With the above configuration, the criteria to be used for defect
detection for each unit of recording (sector or ECC block) is known
by reading the control information, and can be used for performing
maintenance of the data recorded on the disk.
According to a second aspect of the invention, there is provided a
disk device for accessing data on an optical disk, including:
means for determining a criteria for detecting defects according to
the type of data for which defects are to be recorded; and
means for detecting defects using the criteria when data is
recorded on or reproduced from disk.
With the above arrangement, it is possible to use the criteria
suitable for the particular type of data for which defects are to
be recorded.
The detecting means may detect defects with regard to data recorded
on the disk.
In this case the defects may be detected when the data is recorded
on the disk, or when the data is reproduced for verification of the
data having been recorded. When the defects are detected as the
data is recorded, servo defects and header defects can be detected,
but data defects cannot be detected. When the defects are detected
during reproduction for verification, data defects as well as servo
defects and header defects can be detected.
The detecting means may alternatively detect defects when the data
is reproduced. In such a case, if defects are detected, the
reproduction of the data is re-tried. Decision on whether the
reproduction is to be re-tried is made using different criteria
depending on the type of data being reproduced.
The device may comprise means for managing defects on the optical
disk by using non-defective areas of the optical disk in place of
defective areas.
With the above arrangement, the result of the defect detection can
be used in making a decision as to whether the areas found to be
defective should be replaced with non-defective areas.
The determining means may include:
means for storing a plurality of criteria; and
means for selecting one of said plurality of criteria according to
the type of data for which defects are to be detected.
With the above arrangement, the defect criteria can be determined
simply by applying a signal for selecting one of the plurality of
criteria provided in advance, rather than specifying the values
forming the criteria.
The plurality of criteria may include at least a first criteria,
and a second criteria, the second criteria being less strict than
the first criteria, and the selecting means may select the first
criteria when the data for which defects are to be detected is one
for which time restriction with regard to data recording or
reproduction is less strict, and selects the second criteria when
the data for which defects are to be recorded is one for which time
restriction with regard to data recording or reproduction is more
strict.
An example of the data for which time restriction with regard to
data recording or reproduction is less strict is computer data. An
example of the data for which time restriction with regard to data
recording or reproduction is more strict is audio or video
data.
By using a less strict criteria for the audio or video data,
interruption of the audio or video data recording is avoided unless
the defect is of such a degree that the resultant sound or picture
is intolerable.
The determining means may determine the criteria according a
control signal supplied from outside of the device.
The control signal may be supplied from a host device connected to
the disk device.
With the above configuration, the host device can set criteria
which is finely optimized for the type or contents of the data for
which defects are to be detected.
The device may further comprise means for recording data, in units
of recording, on the disk,
wherein
the determining means may determine the criteria for each of the
units of recording, and
the recording means may also record criteria control information
controlling the criteria for each unit of recording, in association
with the each unit of recording.
With the above configuration, the criteria to be used for defect
detection for the data of each unit of recording (e.g., sector or
ECC block) is known by reading the control information, and can be
used for performing maintenance of the data recorded on the
disk.
According to a third aspect of the invention, there is provided an
optical disk for recording data, including an area storing criteria
control information specifying criteria to be used for detecting
defects for data recorded on or reproduced from the disk.
With the above configuration, the criteria to be used for detecting
defects when the disk is accessed is known by reading the criteria
control information recorded on the disk. Accordingly, the
maintenance of the data on the disk is facilitated, and the
interchangeability of the disk is improved since the criteria
control information can be read by any disk device.
The data may be recorded in units of recording, and the criteria
control information indicating the criteria to be used for
detecting detect with regard to each unit of recording may be
recorded in association with each unit of recording.
With the above configuration, the criteria to be used for each unit
of recording, e.g., sector or ECC block, is known by reading the
criteria control information, and can be used for performing
maintenance of the data recorded on the disk.
The information may select said criteria from a plurality of
predetermined criteria.
With this configuration, the amount of control information is
small, since it only needs to specify one of the plurality of
predetermined criteria, rather than specifying values forming the
criteria itself.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a block diagram of an optical disk device of an
embodiment of the present invention;
FIG. 2 is a block diagram of a defect determining means used in the
optical disk device of FIG. 1;
FIG. 3A is a schematic diagram showing examples of deformation of a
groove forming a track;
FIG. 3B is a time chart showing a tracking signal obtained when the
light spot follows the track shown in FIG. 3A;
FIG. 4A is a diagram showing the configuration of a sector on a
DVD-RAM;
FIG. 4B is a schematic diagram showing the signal obtained when the
light spot follows the sector shown in FIG. 4A;
FIG. 5 is a diagram showing an example of errors in an error
correcting block;
FIG. 6 is a table summarizing two sets of defect criteria;
FIG. 7 is a table summarizing three sets of defect criteria;
FIG. 8 is a block diagram of a defect determining means of another
embodiment;
FIG. 9 is a diagram showing an example of procedure followed for
setting defect criteria;
FIG. 10 is a diagram showing another example of procedure followed
for setting defect criteria;
FIG. 11 is a diagram showing the configuration of an example of
defect criteria control information; and
FIG. 12 is a view showing arrangement of information for
controlling defect criteria on an optical disk.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Embodiments of the invention will now be described with reference
to the attached drawings, in which like parts are indicated by like
reference characters.
FIG. 1 is a block diagram of an optical disk device used to
implement the defect management method according to the invention.
A disk rotating means 4 controls rotation of an optical disk 2 for
recording and reproducing data. An optical head servo means 22
performs position control over an optical head 6 such that a light
spot formed by a light beam focused by the optical head 6 follows
the track on the disk 2.
The light reflected from the optical disk 2 representing the data
recorded on the disk 2 is converted in the optical head 6 into an
electrical signal, which is supplied to an address reproducing
means 8 and a signal reproducing means 10. Based on an ID signal in
the header, the address reproducing means 8 reproduces the address
of a sector currently accessed. The detected address is sent to a
drive control means 14. The signal reproducing means 10 reproduces
signals from the signals supplied from the optical head 6 in
accordance with the recording format. A data reproducing means 16
corrects errors in the reproduced signals to produce information,
and outputs information to a host device (not shown) as reproduced
data of the desired logical block.
At that moment, the data reproducing means 16 can recognize a
sector in which the required data is recorded on the basis of
control signals received from the drive control means 14.
Concurrently, the drive control means 14 sends a command to control
the rotational speed of the disk 2, to the disk rotating means 4.
Further, the drive control means 14 determines the position on the
disk, of the sector containing the information to be reproduced,
and sends commands to the optical head access means 20 for moving
the optical head 6 to the position of the sector. The drive control
means 14 also sends commands to control the operation of the servo
system. The optical head access means 20 and the optical head servo
means 22 control the position of the optical head 6 in accordance
with the received commands.
A defect management control information detecting means 18 reads
control information necessary for performing defect management,
from the reproduced data, and obtains information concerning defect
management such as defect management method applied to the disk,
arrangement of spare areas and user areas, status of use of
substitutive sectors, and defect criteria. The information thus
obtained is sent to the drive control means 14 and used for
controlling devices engaged in defect management at the time of
recording or reproducing data.
Incidentally, all the sectors on the disk are numbered with
consecutive addresses from the inner or outer periphery of the
disk. However, the addresses of user data recording sectors are not
consecutive. This is because the physical addresses are assigned
not only to the user data recording sectors, but also to sectors in
spare areas provided for defect replacement and sectors in guard
areas at zone boundaries in the case of a zone format disk.
At the time of performing access from the host device through an
interface, logical block numbers of a file system are used.
Therefore, the disk device needs to perform conversion between a
logical block number and a sector address. The conversion is
carried out by the drive control means 14 in accordance with
received information on defect management.
In writing operation, data sent from the host device is first
inputted to a data recording means 24. The data recording means 24
performs error correction coding on the data in accordance with a
format, and outputs the data as signals to be recorded, with
timings controlled in accordance with the sector addresses on the
disk, having been detected by the control signals supplied from the
drive control means 14.
A signal recording means 26 modulates the received signals in
accordance with a recording format and sends them to the optical
head 6.
The optical head 6 writes the signals into the optical disk 2 by
driving a laser.
At this moment, the optical head 6 is controlled such that a light
spot traces the sector the data is to be recorded, by means of the
optical head access means 20 and the optical head servo means
22.
The drive control means 14 stores defect management control
information detected by the defect management control information
detecting means 18 at the time of disk loading. The logical block
number of the block to be accessed is given by an interface control
signal supplied from the host device, not shown. To be more
specific, the host device sends a recording command specifying the
logical block number of the block where the data is to be written,
and the like, to the disk device, together with the data to be
recorded, or sends a reproducing command specifying the logical
block number of the block from which the data is to be read and the
like, to the disk device.
The drive control means 14 converts the logical block number of the
block to be accessed, to physical addresses, using defect
management information, and sends a command specifying the physical
addresses of the sectors to be accessed, to the optical head access
means 20 and data recording means 24 or data reproducing means 16.
The physical addresses of the sectors currently accessed are
reproduced by the address reproducing means 8, and inputted to the
drive control means 14. Drive control operations such as control
over the optical head access means 20 and data recording means 24
or data reproducing means 16 are performed on the basis of the
detected current address and the target address.
A defect determining means 12 makes judgment as to whether a sector
is defective and is to be replaced. The defect determining means 12
receives information necessary for defect determination on each
sector from the optical head servo means 22, address reproducing
means 8, and data reproducing means 16, and determines presence or
absence of a defect in accordance with a defect criteria set by the
drive control means 14, and reports the results of the
determination to the drive control means 14. When the sector having
been accessed is determined as a defective sector, the drive
control means 14 performs the necessary processes. During
recording, the drive control means 14 interrupts the recording
operation and causes the data of the block to be re-recorded in
substitutive sectors. During verifying reproduction, the drive
control means 14 causes the data of the block having been recorded,
to be re-recorded in substitutive sectors. During reproduction, the
drive control means 14 causes the reproduction to be re-tried.
These operations are pre-programmed into the drive control means
14.
FIG. 2 shows the configuration of the defect determining means 12.
It receives servo error signals such as a tracking error signal and
a focus error signal from the optical head servo means 22. It also
receives a header error signal representing the number of errors in
ID's reproduced for each sector, from the address reproducing means
8. It also receives a data error signal representing the number of
errors in the reproduced data from the data reproducing means
16.
In this embodiment, the defect determining means 12 includes two
defect criteria storing means 34 and 36 for storing different
defect criteria A and B, respectively. The two defect criteria A
and B are inputted to a defect criteria selecting means 38, which
selects and outputs either one of the two criteria A and B in
accordance with a defect criteria setting signal CS. There are
three outputs, Rs, Rd, and Rh. A reference signal Rs for detecting
a servo defect is inputted to a servo defect detecting means 28, a
reference signal Rh for detecting a header defect is inputted to a
header defect detecting means 32, and a reference signal Rd for
detecting a data defect is inputted to a data defect detecting
means 30. They are compared with a servo error signal Es, a header
error signal Eh, and a data error signal Ed in the respective
defect detecting means 28, 32 and 30, to detect presence or absence
of a servo defect, a header defect, and a data defect. A defect
detecting means 40 receives the outputs of the defect detecting
means 28, 32 and 30, and outputs a defect detection signal DF when
at least one of the defects has been detected.
Referring to FIG. 3A and FIG. 3B, detection of a servo defect will
be described. For recording data, a track which has a substantially
uniform width Wt (the track is actually circular or spiral, but the
short part of the track illustrated can be treated as straight) is
used. The track is formed of a continuous guide groove or the like.
Consideration will be given to the case where the track is deformed
at points X and Y. Such deformation may be caused due to dirt
introduced during fabrication of a master disk or a substrate,
irregular operation of a manufacturing machine, unevenness of a
formed substrate, and other minor irregularities. Tracking control
is performed such that a light spot follows the centerline 42c of
the track shown by a chain line in FIG. 3A, and a tracking error
signal Et shown in FIG. 3B is obtained. The tracking error signal
Et is zero when the light spot is following the centerline 42c of
the track. When the light spot deviates from the centerline 42c,
the tracking error signal Et deflects either positively or
negatively depending on the direction and the amount of deviation.
Where there is a deformation of the track and the centerline 42c of
the track is bent abruptly, since the light spot cannot follow the
abrupt bending, the light spot deviates from the centerline
42c.
At point X, there is a deflection in the tracking error signal Et
due to the deformation of the track. At point Y, there is also a
deflection in the tracking error signal Et due to meander of the
track. If the tracking error tolerance limit Rtb shown by the
broken line in FIG. 3B is given as a reference for determining a
servo defect, a servo defect is recognized at point Y. If a more
strict tracking error tolerance limit Rta shown by the chain line
in the figure is given, servo defects are recognized both at points
X and Y.
The tracking error tolerance limit Rta corresponds to the value of
the tracking signal Et when the deviation of the light spot is
one-fourth the tracking width Wt, and the tracking error tolerance
limit Rtb corresponds to the value of the tracking signal Et when
the deviation of the light spot is one-eighth the tracking width
Wt.
For instance, if the level Rta at the chain line is used as the
defect criteria A, and the level Rtb at the broken line the figure
is given as the defect criteria B, it is possible to perform servo
defect determining process at two different levels. Incidentally,
the recording track may not be a continuous groove. In a disk, such
as a DVD-RAM, where user data recording areas are formed of lands
and grooves, and no groove is formed at the header parts, which are
formed of pre-pits only, it is sufficient to perform a servo defect
detection only for areas where a groove continues.
Servo defect detection can be performed with regard to a focus
error signal, in the same way as the tracking error signal.
FIG. 4A shows the configuration of a sector in a groove track in a
DVD-RAM, and FIG. 4B shows the waveform of the signal reproduced
from the sector shown in FIG. 4A. These drawings will be used for
describing the detection of header defect. A recording sector of a
DVD-RAM includes a header area having a sector address and the like
at the beginning, followed by a data area for recording user data.
The header area includes four ID's, indicated as ID1 to ID4 each
containing address information representing a sector address. In
the sector shown in FIG. 4A, ID1 and ID2 are displaced one-half the
track width Wt toward the outer periphery of the disk, and are
shared with a sector in the outer adjacent land track, while ID3
and ID4 are displaced one-half the track width Wt toward the inner
periphery of the disk, and are shared with a sector in the inner
adjacent land track.
In a land track not shown, ID1 and ID2 are displaced by one-half
the track width Wt toward the inner periphery of the disk, and are
shared with a sector in the inner adjacent groove track, and ID3
and ID4 are displaced by one-half the track width Wt toward the
outer periphery of the disk, and are shared with a sector in the
outer adjacent groove track. The waveform of the signal reproduced
from the header area and the data area in a sector in a land track
is also shown in FIG. 4B.
The data area following the header is in a groove or a land, and
contains a synchronous signal (SYNC), control information (CI),
user data, and an error-correcting codes, and a buffer, which are
recorded successively in this order. The control information CI
consists of a small amount of information (such as the data number
of the sector), other than user data.
The size of user data, together with the control information, in
one sector is 2 KB (kilobytes), and error-correcting coding is
performed taking the user data and the control information of 32 KB
in 16 successive sectors, as a unit, wherein error-correcting codes
are added to the to form an ECC block.
The error-correcting codes are distributed over the 16 sectors.
The sector address can be obtained if even one of the four ID's in
a header is read correctly. In criteria B, if none of the four ID's
is read correctly, the sector is found have a header defect, and if
two or more sectors within an ECC block are found to have a header
defect, the ECC block is found to have a header defect. In criteria
A, if not more than one of the four ID's is read correctly, the
sector is found have a header defect, and if one or more sectors
within an ECC block are found to have a header defect, the ECC
block is found to have a header defect.
A sector found to be non-defective according to criteria A has at
least two correctly readable ID's. This make it more likely that at
least one ID will remain correctly readable even if the disk is
later soiled or degraded, or transferred to another disk
device.
In this way, it is possible to perform header defect determination
with two different levels.
FIG. 5 shows the structure of an ECC block in a DVD-RAM. This
drawing is used to describe the data defect detection. In the data
recording means 24, the 23 KB data for 16 sectors are arranged in
the form of matrix of 172 bytes in the row direction by 192 bytes
in the column direction. A 16-byte parity outer code PO in the
column direction is added to each column, and then 10-byte parity
inner code PI in the row direction is added to each row.
Thus, a product code, which is a Reed-Solomon code, of 182
bytes.times.208 bytes is formed.
When the data is recorded on the optical disk 2, the PO rows are
interleaved with the other rows so that the error-correcting code
bytes are evenly distributed over all 16 sectors of the ECC
block.
At the time of reproduction, the data reproducing means 16
rearranges the reproduced signal into a matrix of 182
bytes.times.208 bytes, and first detect and correct any errors of
each row by means of the 10-byte inner code PI. The inner code PI
is capable of correcting errors in up to five bytes per row, and
detecting errors in up to ten bytes per row.
Next the 16-byte outer code PO is used to detect and correct any
remaining errors. The outer code PO is capable of correcting errors
in up to 8 bytes per column, and detecting errors in up to 16 bytes
per column. These error detecting and correcting capabilities can
be improved by repeating the PI-PO error correction process,
although the additional repetitions require additional circuitry
and additional time.
When a large number of errors are detected and corrected, it
becomes likely that some of the corrections are wrong, the
corrected data differing from the original data. Criteria A and B
are therefore set, for example, as follows. In criteria A, a row is
considered to have a data defect if errors are detected in at least
four bytes, which is close to the error-correcting limit of the PI
code, and an ECC block is considered to have a data defect if it
has at least eight rows having a data defect. In less strict
criteria B, a row is considered to have a data defect if errors are
detected in at least eight bytes, which is close to the repeated
error-correcting limit of the PI code, and an ECC block is
considered defective if it has at least eight rows having a data
defect. When an ECC block is considered to have a data defect, all
sixteen of its constituent sectors are replaced.
In this way, it is possible to perform data defect determination
with two different levels.
In FIG. 5, row three has errors in four bytes, indicated by x's.
This row is deemed to have a data defect under criteria A, but not
under criteria B.
In this way, the presence or absence of defect in each sector can
be determined with respect to each of the servo defect, the header
defect, and the data defect, according to the defect criteria
supplied to each defect detecting means. FIG. 6 summarizes the
defect criteria A and B described above described as examples for
the respective defects. The set of criteria A are stored in the
criteria storing means 34, while the set of criteria B are stored
in the criteria storing means 36. It is then possible to switch
between the two levels of criteria A and B by means of the criteria
selecting means 38, according to the criteria setting signal
CS.
In the case of recording computer data, a high reliability is
required so that the data once recorded are not lost or changed.
For this reason, verifying reproduction is often effected at the
time of recording. Accordingly, during recording and during
verification production, the strict criteria A is applied to ensure
that the correct data is recorded.
In contrast, in the case of audio or video data, continuous
recording at a high transfer rate is required. Accordingly,
verifying reproduction is often omitted, ignoring data defects.
Even if some defects occur during recording, as long as occurrence
of the defects is of such a degree that the defects can be
corrected or concealed later at the time of reproduction, it is
preferable to continue recording operation ignoring the defects,
since it will improve the performance and the operability as a
recorder. For this reason, the criteria set for servo defects and
header defects are set at a less strict level at which the recorded
data can be corrected or concealed.
When the two different defect criteria A and B available, the
strict criteria A is used for recording computer data, while the
less strict criteria B is used for recording audio or video
data.
There are situations where more than two different levels of
reliability are required depending on types of data to be recorded.
For instance, there is a situation where three different levels are
required, one for recording computer data, another for recording
important audio or video data, and the last one for recording
normal audio or video data. In such a situation, as shown in FIG.
7, provision is made to enable switching among three different
defect criteria A, B, and C. Criteria A and B are the same as those
described with reference to FIG. 6, and are used for recording
computer data and for recording normal audio or video data,
respectively.
The criteria C is used for recording important audio or video data,
and therefore, it has strictness intermediate between the criteria
A and B. In the criteria C, the allowable deviation in tracking
error is one-sixth the track width Wt, and an ECC block is found to
have a header defect if all four ID's are unreadable in any one
sector. Regarding data defects, criteria C and A are the same.
To use the three different sets of defect criteria, the defect
determining means 12 should have an additional criteria storing
means, in addition to the members shown in FIG. 2, and the criteria
selecting means 38 should be able to select among the criteria A, B
and C supplied from the above-mentioned additional criteria storing
means, as well as the criteria storing means 34 and 36 in FIG. 2,
in accordance with the criteria setting signal CS.
FIG. 8 shows another embodiment of the defect determining means 12.
The configuration of FIG. 8 is different from the configuration of
FIG. 2 in that the criteria storing means 34 and 36, and the
criteria selecting means 38 which makes selection according to the
criteria selecting signal CS shown in FIG. 2 are replaced with a
defect setting and storing means 46 which makes setting according
to the criteria selecting signal CS.
The defect criteria to be applied is supplied from a host device
(not shown) through an interface to the drive control means 14. In
response, the drive control means 14 generates a criteria setting
signal CS specifying the criteria.
In the defect determining means 12 of FIG. 2, the defect criteria
stored in the respective criteria storing means are fixed. However,
in practical use, it may be desirable that the host device which
controls the disk device (recording device) can flexibly vary the
criteria so as to optimize the reliability and the transfer rate,
depending on the nature, type, characteristics, and the degree of
importance of the data to be recorded. For instance, a
countermeasure for errors may be provided in the application
software or file system. That is, error correcting coding may be
applied before transmitting the data to the disk device at a
predetermined rate. In this case, the defect management at the disk
device is not so important, and the capability of continuous
real-time recording at a high data transfer rate may be
important.
The embodiment described above can meet with these
requirements.
An embodiment of procedure followed in setting a defect criteria
will be described with reference to FIG. 9. First, the host device
sets the defect criteria to be used, according to type or contents
of the data to be recorded. Then, a command for setting the
criteria is sent from the host device to the disk device (drive).
The disk device selects or sets the criteria upon reception of the
command accordingly. In the system shown in FIG. 2, the command
sent from the host device to the disk device is one for merely
specifying selection between the criteria A and B. In the system
shown in FIG. 8 in which the defect criteria can be set, the system
is so configured that the defect criteria can be set arbitrarily at
the host device, and the command indicates the defect criteria set
at the host device. Details of the command for setting the defect
criteria may be one which will be described later with reference to
FIG. 11, in which the defect criteria control information can
select one among a plurality of criteria independently, for each of
the servo defect, header defect, and data defect.
The host device then sends a recording command together with the
data to be recorded. Upon reception of the command, the disk device
records data in the specified sectors, and performs the defect
management using the defect criteria set in the manner described
above, and reports the results of the defect management to the host
device. The host device terminates a series of recording when it
confirms that recording has been completed correctly. If the
recording has been done incorrectly, a predetermined process
(re-writing or informing the user) for dealing with the
incorrectness is carried out.
According to the procedure of FIG. 9, the host device, which knows
the contents of the data to be recorded, sets the defect criteria
finely optimized according to the type or contents of the data. It
is therefore possible to provide flexibility for obtaining an
optimum combination of reliability and transfer rate according to
the intended use of the data.
FIG. 10 shows another embodiment of a procedure followed for
setting a defect criteria. In this embodiment, a command which sets
a defect criteria and also instructs data recording is sent. First,
the host device determines a defect criteria to be used in
accordance with the type or contents of the data to be recorded,
and then prepares the data to be recorded. This order may be
reversed.
Then, the host device sends the recording command which also sets
the defect criteria, to the disk device. In accordance with the
designated defect criteria, the disk device selects or sets the
criteria. The designation of the setting sent from the host device
to the disk device may be one for specifying selection among a
plurality of preset criteria (such as between the criteria A and
B), or one for setting an arbitrary criteria.
The disk device records the data received together with the
command, on the disk, while performing defect management in
accordance with the defect criteria which has been set as described
above, and informs the host device of the result. According to this
embodiment, it is possible to obtain an optimum combination of
reliability and transfer rate depending on the intended use of the
disk, as in other embodiments described earlier. Moreover, because
the number of commands transferred is reduced, the overhead is
reduced, and the possibility of the transfer rate becoming lowered
is reduced.
A manner of recording control information representing the defect
criteria designated at the time of data recording, in every sector
on a disk will now be described. FIG. 11 shows the configuration of
a defect criteria control information. With this configuration, one
of four different criteria can be specified for each of the servo
defect, the header defect and the data defect independently, by
using one byte.
The most-significant bit b7 indicates the mode of designation of
the defect criteria. If the value of bit b7 is "1", the mode
designated by other bits of the control information byte is used,
while if the value is "0" the default criteria which the disk
device has is used ignoring the other bits of the control
information byte.
The next bit b6 indicates the range within which the defect
criteria should be applied. If the value of bit b6 is "1", the mode
set by other bits in the control information byte of are applied
for each unit of recording, e.g., each sector or block. If the
value of bit b6 is "0" the same criteria is to be applied over the
entire surface of the disk.
The next two bits (b5 and b4) indicate the criteria applied for the
servo defect, among the four criteria. If the combined value of
bits b5 and b4 are "11" the tracking error tolerance above which
the servo defect is recognized is one-forth the track width Wt. If
the combined value is "10" the tolerance is one-sixth the track
width Wt. If the combined value is "01" the tolerance is one-eighth
the track width Wt. If the combined value is "00" the tolerance is
one-tenth the track width Wt.
The next two bits b3 and b2 indicate the defect criteria to be
applied for the header defect, among the four criteria. If the
combined value of the bits b3 and b2 is "11" the ECC block is found
to have a header defect if all four ID's are unreadable at two or
more of its sectors. If the combined value is "10" the ECC block is
found to have a header defect if three or more ID's are unreadable
at two or more of its sectors. If the combined value is "01" the
ECC block is found to have a header defect if all four ID's are
unreadable at one or more of its sectors. If the combined value is
"00" the ECC block is found to have a header defect if three or
more ID's are unreadable at one or more of its sectors.
The last two bits b1 and b0 indicate the defect criteria to be
applied for the data defect, among the four criteria. If the
combined value of the bits b1 and b0 is "11", the ECC block is
found to have a data defect if at least 16 of its rows have errors
in at least 8 bytes each. If the combined value is "10", the ECC
block is found to have a data defect if at least 8 of its rows have
errors in at least 8 bytes each. If the combined value is "01", the
ECC block is found to have a data defect if at least 8 of its rows
have errors in at least 4 bytes each. If the combined value "00",
the ECC block is found to have a data defect if at least 6 of its
rows have errors in at least 4 bytes each.
The above described defect criteria control information can be
located in each sector which constitutes a minimum unit of
recording. In a DVD-RAM, a one-byte area may be reserved in the
control information area located at the beginning of the data area
shown in FIG. 4. The criteria may be set for each sector
separately. The same defect criteria control information may be set
in all the sectors within the same ECC block, or in predetermined
sectors, so that the defect criteria control information is
repeatedly recorded, and the range within which the same defect
criteria should be applied may be made to coincide with the unit of
error correction (ECC block).
The provision for enabling setting the finely optimized criteria
improves the utility for the user in multimedia applications in
which the audio or video data and computer data are intermixed with
each other. It should be noted that the defect criteria to be
applied to the respective data can be switched at the system (host
device) depending on the contents of the data, and it is possible
to realize a flexibility for obtaining the optimum combination of
the reliability and transfer rate.
It is possible to pre-select a defect criteria to be used in
recording on a disk, and record the criteria as defect criteria
control information on the disk, before the disk is used. FIG. 12
shows an example of arrangement of control information areas, and a
data recording region including user areas and spare areas, and
arrangement of defect criteria control information in the control
areas. The data recording region is divided into groups, each of
which includes a user area and a spare area. The control
information areas are disposed near the inner and outer peripheries
of the disk, and the same control information is recorded on the
respective control information areas.
In a known example, a defect management method is recorded in a
control information area. In contrast, according to this
embodiment, defect criteria control information is stored in a
control information area. At the time of starting a disk, the disk
device reads the defect criteria control information to know the
defect criteria. If the defect criteria suitable for the intended
use, such as computer data, audio or video data, or the like is
recorded, the defect determination according to the defect criteria
can be made.
If one bit is provided in the control information area for
recording the defect criteria control information, it is possible
to record two sets of defect criteria, and selectively use them.
For recording three or four sets of defect criteria, and using them
selectively, two bits should be provided in the control information
area. If one byte is provided in the control information area, it
is possible to select one of the criteria for each of the servo
defect, data defect and header defect, and to specify a combination
of specific defect criteria for the respective types, as described
with reference to FIG. 11.
With such a provision, if the information is recorded once at the
time of initialization of the disk, the defect criteria can be
applied to all the data thereafter recorded on the disk. It is
therefore possible to eliminate to need to set the defect criteria
each time the data is recorded. Accordingly, the recording can be
effected at a high speed, and in a simple manner.
* * * * *